Lifeline AGM's Fully Charged Voltage?

[motion30]

Originally Posted by kmacdonald

Trojan recommends a maximum absorption time of 4 hours. Some chargers use the 4 hour time limit.

But if I am not mistaken Trojan specifies higher absorption voltage, yes

[kmacdonald]

Originally Posted by a64pilot

See that’s the thing.
It makes as much sense as saying Island Packet recommends putting 30 gls into the tank whenever you refill. How about if you only used 10? What if you used 50?
Then to further confuse things the 4 hour time limit doesn’t know how big your charger is, so depth of discharge, and actually house loads and charger size can change that 4 hours.
You need to watch your trailing Amps and determine for yourself, what your bank, with your charge source and your usage is.
Or your just shooting in the dark and hoping to get it right, which with four hours, is unlikely.

Yep, I know. That recommendation doesn't make much sense. If you used their recommendation of a charger rated at 12% of C you wouldn't get a 50% SOC battery back to full even at 100% charge efficiency. Maybe they are implying to use a bigger charger that will get you close to full in 4 hours or don't cycle as deeply. It's as clear as mud.

[kmacdonald]

Originally Posted by motion30

But if I am not mistaken Trojan specifies higher absorption voltage, yes

14.7 to 14.8 volts for most of their LA batteries.

[noelex 77]

Originally Posted by kmacdonald

Yep, I know. That recommendation doesn't make much sense. If you used their recommendation of a charger rated at 12% of C you wouldn't get a 50% SOC battery back to full even at 100% charge efficiency. Maybe they are implying to use a bigger charger that will get you close to full in 4 hours or don't cycle as deeply. It's as clear as mud.

4 hours is the recomended maximium absortion time, not the total charging time.

4 hours is very long absorption time. It is hard to imagine any lead acid battery needing more than this.

A charger with a high output (relative to the battery size) needs a longer, not a shorter, absorption time which is why solar regulators with their relatively low effective charge current usually need reasonably short absorption times.

[kmacdonald]

Originally Posted by noelex 77

4 hours is the recomended maximium absortion time, not the total charging time.

4 hours is very long absorption time. It is hard to imagine any lead acid battery needing more than this.

A charger with a high output (relative to the battery size) needs a longer, not a shorter, absorption time which is why solar regulators with their relatively low effective charge current usually need reasonably short absorption times.

Yes, the majority of charging is done during the bulk phase. The lower the charge current during bulk the higher the SOC will be at the end of bulk charging. With high current alternators, the SOC at the end of the bulk phase will be much lower and require a lot longer absorption phase. If you want to get to 100% SOC there's not a lot of benefit of a super high current alternator.

[john61ct]

With higher-CAR chemistries at high amp rates, charging can hit the V setpoint in the first half-hour, even at low SoC.

Since total charge time is not reduced by much, that means a **much** longer Absorb time before hitting 100% Full as per endAmps,

than in a low-current scenario like solar.

[john61ct]

wrt Trojan specifically, from Maine Sail

______
The part most miss is that this voltage guidance is qualified by stating: "If charging time is limited, contact Trojan Technical Support for assistance."

If you contact them, and get someone who knows something, they will tell you that for a PSOC use application an absorption of 14.8V -15.0V is more optimal and this means a .1V higher bv than Av for a bulk transition on a Balmar reg. Even an absorb of 14.7V will help the bank last longer than 14.6V but 14.8V is even better.

I've been setting FDC up anywhere between about 15.0V and an & 14.8V for about 15 years for absorption. Cycle life has been rather dramatically improved and they consistently outlast the boats I see set up for old school 14.2V - 14.6V..

http://www.cruisersforum.com/forums/...on-201841.html

[john61ct]

Originally Posted by a64pilot

See that’s the thing.
It makes as much sense as saying Island Packet recommends putting 30 gls into the tank whenever you refill. How about if you only used 10? What if you used 50?
Then to further confuse things the 4 hour time limit doesn’t know how big your charger is, so depth of discharge, and actually house loads and charger size can change that 4 hours.
You need to watch your trailing Amps and determine for yourself, what your bank, with your charge source and your usage is.
Or your just shooting in the dark and hoping to get it right, which with four hours, is unlikely.

Absolutely.

I think such guidelines "50% DoD", "max 4 hours" are intended for the vast majority of uninformed users, not those closely calibrating their charge cycle, e.g. measuring trailing amps.

Once you get to that level of knowledge and gear, you are free to make your own informed decisions.

[a64pilot]

Originally Posted by noelex 77

4 hours is very long absorption time. It is hard to imagine any lead acid battery needing more than this.

From Maine Sails how long to charge a battery write up.
.15C is neither large or small, pretty much common, looks to be 4.5 hours of absorption.



From my observation, you can put Solar Charger time to 10 hours if you want to, your going to be lucky to get more than a couple hour of absorption, most charging is done in bulk, because the charge source is way to small to reach Absorption voltage, you can of course fully charge a battery and never reach absorption voltage, just takes a long time is all.
Due to depth of discharge being one variable and Solar output being another, a timer can’t be relied on, you have to watch the trailing amps unfortunately, there just isn’t another way that I am aware of.

The timer method can work of course IF you have on average excessive time, an hour or so excess absorption voltage isn’t likely to harm anything and yet will ensure on most days that your as fully charged as you can be.
For me Absorption on Solar is a mute point as long as we are aboard and using the bank, cause I can’t get to 100% SOC, both my battery monitors will say I am, but the trailing amps come up short.

[john61ct]

All correct, but (nit pick) technically 100% Full is defined by trailing current **at** Absorb V.

Say AbsV is 14.40 and endAmps is .005C.

Maybe 0.0A trailing current at 14.38 get to the same point, but maybe not.

If you increase V to 14.40 and .02C flows, you (technically nit pick) did not get **quite** to 100% Full.

[a64pilot]

Originally Posted by rom

Honestly a64, if you can get 10+ years with very little attention, why would you spend so much time & energy to reach true 100% every 2 days ??

To make a long story short I come from an aircraft manufacturing background, that gave me access to the Concorde battery corporation that maybe I wouldn’t have if I hadn’t.
Concord is an aircraft battery, and the company that also manufacturers the Lifeline battery.

Anyway with discussions with them is how I came up with the twice a week fully charged, once a month equalization thing.
It was not knowledge I had, it was given to me with explanations.
They said I should get 5 yrs of service out of a bank if Indo that, of full time cruising.
I can only postulate that your bank either met the definition of dead years ago however was still hanging in there well enough or you spend a lot of time plugged in, or more likely both.
Many people nurse a bank for years past it’s legal death if you will, and don’t replace one until it completely fails.
Nothing wrong with that either, it’s I guess sort of like to a racer most of us sail happily every day on sails that are way past gone too.

Lifeline bank is expensive, especially after you leave the US, so I feel spending a penny here and there may hopefully save a dollar later.
I’m hoping this bank will take me until LFP is more mainstream and not so experimental.

[Exile]

Originally Posted by a64pilot

From my observation, you can put Solar Charger time to 10 hours if you want to, your going to be lucky to get more than a couple hour of absorption, most charging is done in bulk, because the charge source is way to small to reach Absorption voltage, you can of course fully charge a battery and never reach absorption voltage, just takes a long time is all.
Due to depth of discharge being one variable and Solar output being another, a timer can’t be relied on, you have to watch the trailing amps unfortunately, there just isn’t another way that I am aware of.

The timer method can work of course IF you have on average excessive time, an hour or so excess absorption voltage isn’t likely to harm anything and yet will ensure on most days that your as fully charged as you can be.
For me Absorption on Solar is a mute point as long as we are aboard and using the bank, cause I can’t get to 100% SOC, both my battery monitors will say I am, but the trailing amps come up short.

Didn't you say you had 1kw of solar, or am I confusing your set-up with someone else? If that's the case, do you then need to resort to your Honda generator to get to 100% SOC? (While you're away from the dock that is).

[noelex 77]

0.15c is not a typical charge rate. For your 660 Ahr battery bank this would require a 100 A charge rate. The charger has to also run the loads, so the charge source needs to deliver 100 A + whatever loads you are running. I doubt your solar, battery charger, or Honda can deliver this type of charge current.

The example shows that if you have a charge rate this high and you deplete your batteries down to 50% and your batteries specify a very low 0.5 % end amp setting, then a 4:24 absorption time might be needed.

I think this illustrates that this type of absorption time would only be needed if you have a very high charge rate coupled with a very depleted battery. These are not typical conditions.

This is why Trojan cannot envisage an absorption time of longer than 4 hours. Hence the recommendation that this is a maximum value. Trojan specify a more typical 2% end amp setting. The graph (if it applies to Trojan batteries) shows this would be reached well before 4 hours.

[a64pilot]

Well, when I’m running Diesel, I charge at 185 amps, which will kick me out of Bulk in about 20 mins, if I’m at 50% SOC which I never am, so it’s likely I only stay in bulk for less than 10 mins. Solar adds to that 185 amps, that is shorepower chargers only and I could crank the engine for another 175 amps, be silly of course, but I could.
On Solar alone, I barely reach absorption, so I’d need 4+ hours with 185 amps charger, and maybe only a couple of hours with 1000W Solar.
This assuming 50% SOC.
You want high charge rates with a Lifeline bank, not trickle charging whenever possible. You can realistically have to big a Charger, Lifeline says up to 5C I think, which is over 3000 amps, and that’s just not happening anywhere but a Lab I don’t think.

Plus, unless mistaken the thread is about Lifeline AGM, not Trojan’s?

[kmacdonald]

I know one of my batteries will NEVER get to 0.5%C end amps at 14.8 volts no matter haw long it's connected and it's a fairly new battery. The 0.5%C current might be more than we can hope for. Maybe a more realistic 1 or 2%C figure might be more appropriate.